The officer whose gun shots set off the deadly 50-shot barrage that killed Sean Bell in 2006 was fired by NYPD yesterday — and three other officers involved in the infamous shooting were forced into retirement, cops said.

Police Commissioner Ray Kelly made the decision to fire Detective Gescard Isnora after an administrative judge in December found Isnora guilty of departmental violations.

“There was nothing in the record to warrant overturning the decision of the department’s trial judge,” Deputy Commissioner of Public Information Paul Browne yesterday.

Detectives Michael Oliver, Marc Cooper and Lt. Gary Napoli all are being forced to retire.

An administrative judge found Isnora guilty of violating department guidelines by panicking and blowing his cover when he blasted 11 shots outside a Queens strip club in 2006.

Officer Michael Carey, who testified that he opened fire after he heard Isnora yell “Gun!” was cleared of all departmental charges.

All cops involved were cleared of criminal charges.

The president of the Detectives Endowment Association last night slammed Isnora’s firing.

“I think the decision is disgraceful, excessive and unprecedented,” Mike Palladino said. “Stripping a cop of his livelihood and retirement is usually reserved for rogue cops who go bad, not for cops who act within the law and whose actions were justified by a court of law and the US Department of Justice.”

Meanwhile, a source close to the Bell family told The Post: “There’s no joy in it,” referring to the firing.

Last night Bell’s father, William expressed that lack of enthusiasm for the NYPD’s move.

“They’re surviving,” he said, referring to the officers involved in the shooting. “But I have to live with the pain. It’s not a fair and just outcome.”

In 2006, the four cops fired 50 bullets at a car carrying the unarmed Sean Bell and two friends outside a Jamaica strip club early on the morning Bell was to married.

Isnora had testified that he followed Bell and his friends from the jiggle joint because he thought Bell’s pal Joseph Guzman was going to retrieve a gun.

The canned detective said he opened fire after he was clipped by Bell’s car and saw Guzman’s arm go up, and testified that he never actually saw a gun.